Understanding batteries in Mac notebooks

MacBook, MacBook Air, and MacBook Pro computers come with lithium polymer batteries to provide maximum battery life in a compact space. In order to fully understand battery technology and battery life, it's good to know common battery terminology.

Cycle count: Batteries are expected to function for a certain number of cycles. This number represents the sum of total and partial discharge cycles throughout the life of the battery. You can see the cycle count limit for your computer by reviewing Determining battery cycle count for Mac notebooks.

Full charge capacity: Measured in mAH (milliampere-hours), this refers to the amount of power the battery is capable of containing, less the energy required to shut down the device. This number lowers as the battery becomes depleted with usage and age.

Remaining charge capacity: This number represents the current amount of power left in the battery as measured in mAh (milliampere-hours). Using the computer when not connected to AC power will cause this number to lower as power is depleted from the battery.

Consumed / depleted: Consumable parts are those that deplete over time as their internal components are used. Batteries, due to their chemical components, are considered consumables, and slowly over time they lose their ability to hold a charge. If the cycle count on a battery exceeds its expected limit, the battery is considered consumed.

Defective: Batteries are considered defective when they stop working due to a defect in materials or workmanship, or due to a manufacturing defect. Defective batteries are covered under Apple's one-year limited warranty and extended-service contracts.

Runtime: The length of time a battery will power a computer. Battery runtime depends on the amount of power being consumed. The runtime is affected by the full charge capacity and cycle count of a battery as well as the load put on the system the battery is powering.

Load: The amount of activity being performed by a task or tasks. Certain power-intensive processes place a heavier load on the battery and result in a much-reduced runtime per charge.

The battery status menu

Your primary resource for viewing battery status is the battery status menu. The battery status menu shows you how much charge your battery has and whether it's currently charging. This menu is at the right side of the menu bar:

The battery status menu updates frequently and changes depending on your screen brightness and system workload. You may see the time remaining drop significantly, for instance, if it updates while opening a very large file or starting up an application. It's important to remember it's an estimate based on what your computer is doing at the specific time it updates.

To see the health of your battery, hold the Option key and click the battery icon:

You'll see one of the following status indicators:

Normal: The battery is functioning normally.

Replace Soon: The battery is functioning normally but holds less charge than it did when it was new. You should monitor the health of the battery by checking the battery status menu periodically.

Replace Now: The battery is functioning normally but holds significantly less charge than it did when it was new. You can safely continue using your computer, but if its lowered charging capacity is affecting your experience, you should take it to an Apple Store or Apple-authorized service provider.

Service Battery: The battery isn’t functioning normally. You can safely use your Mac when it's connected to an appropriate power adapter, but you should take it to an Apple Store or Apple-authorized service provider as soon as possible.

While some third-party apps report on battery health conditions, the data reported by these apps may be inaccurate and isn't a conclusive indication of actual diminished system run time. It's recommended that you rely on the information reported in the battery health menu (shown and described above).

Optimizing battery life

Your notebook battery life depends on your computer's configuration and how you're using the computer. Here are some settings and steps you can take to get the most from of your MacBook, MacBook Pro, or MacBook Air battery.

Adjusting display brightness

Compared to any other setting on your computer, your screen brightness can have the greatest impact on battery life. Press the F1 key to dim the screen until the brightness is as low as possible and the screen is still comfortable to view. You can also set your display brightness under Apple menu > System Preferences > Displays.

Graphics performance and its impact on battery life

MacBook Pro 15-inch and 17-inch notebooks commonly include two graphics processors or GPUs. You may see them documented as a discrete GPU and an integrated GPU. The discrete GPU generally provides substantial performance at the expense of high power draw. The integrated GPU allows for optimal battery life but in most cases does not have the performance of a discrete GPU. For optimal battery life, use the integrated GPU. The following articles provide steps for using these different GPUs and information on what could be driving unexpected use of the discrete GPU.

Energy Saver in System Preferences

The Energy Saver pane in System Preferences has many options to help improve the battery life on your Mac notebook when idle. For instance, setting your display to sleep when idle temporarily turns off the backlight and significantly improves the battery life.

The example above is from OS X Mountain Lion v10.8.4. Some features such as Automatic graphic switching and PowerNap are not available on all Mac notebooks or versions of OS X.

Disabling features and technologies that use power

Mac notebooks have a number of integrated technologies which can have a significant effect on battery power.

Disable AirPort or Bluetooth from their menu bar icons or in System Preferences (Network and Bluetooth respectively). This will help save power.

External USB, FireWire, ThunderBolt, SD card, and Expresscard devices added to your notebook may also draw power and should be disconnected for optimal battery performance.

Eject any CDs or DVDs from the integrated SuperDrive (if available on your notebook) to avoid the drive spinning periodically.

Troubleshooting batteries

A great place to start when troubleshooting battery issues is the built-in diagnostics that are available on your Mac notebook. Follow the steps in these articles:

If Apple Diagnostics tells you that your battery requires service and cites reference code PPT004, you should confirm this issue by running Apple Diagnostics over the Internet, which uses the latest diagnostic information. To do this, turn off your Mac by choosing Shut Down from the Apple () menu. Then press the power button to turn on your Mac. Immediately press and hold Option-D until Apple Diagnostics begins.

Learn how apps can affect Mac battery performance. Check Activity Monitor for any malfunctioning software processes, especially after installing software updates or a new operating system. Installing updates is important to ensure optimal performance for all applications.

If you're still having battery runtime issues after optimizing your computer's performance and checking for malfunctioning software processes, test in Safe Mode. Safe Mode limits the active items on the system and allows testing in a more minimal environment. If the battery life is better in Safe Mode, you may need to do further software isolation for the items disabled by Safe Mode to determine what the power draw is while not operating in Safe Mode.

My battery won't charge to 100%

Occasionally, the battery may not show a full charge (100%) in OS X, even after the power adapter has been connected for an extended period of time. The battery may appear to stop charging between 93 percent and 99 percent. This behavior is normal and will help to prolong the overall life of the battery.

My battery isn't recognized

If the battery in your MacBook, MacBook Air, or MacBook Pro is fully drained of power, the battery will put itself into a low power state to preserve its ability to charge in the future. Connect your Mac Notebook to AC power and allow it to charge for at least five minutes. If the connect to power screen persists after charging for five minutes, reset the SMC.

The low battery warning doesn't display

If you don't receive a warning when your battery has a low charge, generally reported at or under 15%, it may be because the battery menu bar icon is disabled. Follow these steps to enable the battery status menu item:

Portables using OS X Mavericks v10.9 or later display the low battery warning when the battery has approximately 10 minutes of power remaining. Earlier versions or OS X instead report it at 15% or less.

Servicing the battery in your Mac notebook

MacBook, MacBook Air, and MacBook Pro computers with built-in batteries should only have their batteries replaced by an Apple Authorized Service Provider or Apple Retail Store. Attempting to replace a built-in battery yourself could damage your equipment, and such damage is not covered by warranty.

Battery warranty information

Your Apple One Year Limited Warranty includes replacement coverage for a defective battery. If you purchased an AppleCare Protection Plan for your Mac notebook, Apple will replace the notebook battery at no charge if it retains less than 80 percent of its original capacity. If you don't have coverage, you can have the battery replaced for a fee.

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